/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.http.client.reactive;

import java.net.URI;
import java.util.function.Function;

import io.netty.buffer.ByteBufAllocator;
import reactor.core.publisher.Mono;
import reactor.netty.NettyInbound;
import reactor.netty.NettyOutbound;
import reactor.netty.http.client.HttpClient;
import reactor.netty.http.client.HttpClientRequest;
import reactor.netty.http.client.HttpClientResponse;
import reactor.netty.resources.ConnectionProvider;
import reactor.netty.resources.LoopResources;

import org.springframework.http.HttpMethod;
import org.springframework.util.Assert;

/**
 * Reactor-Netty implementation of {@link ClientHttpConnector}.
 *
 * @author Brian Clozel
 * @see reactor.netty.http.client.HttpClient
 * @since 5.0
 */
public class ReactorClientHttpConnector implements ClientHttpConnector {

    private final static Function<HttpClient, HttpClient> defaultInitializer = client -> client.compress(true);


    private final HttpClient httpClient;


    /**
     * Default constructor. Initializes {@link HttpClient} via:
     * <pre class="code">
     * HttpClient.create().compress()
     * </pre>
     */
    public ReactorClientHttpConnector() {
        this.httpClient = defaultInitializer.apply(HttpClient.create());
    }

    /**
     * Constructor with externally managed Reactor Netty resources, including
     * {@link LoopResources} for event loop threads, and {@link ConnectionProvider}
     * for the connection pool.
     * <p>This constructor should be used only when you don't want the client
     * to participate in the Reactor Netty global resources. By default the
     * client participates in the Reactor Netty global resources held in
     * {@link reactor.netty.http.HttpResources}, which is recommended since
     * fixed, shared resources are favored for event loop concurrency. However,
     * consider declaring a {@link ReactorResourceFactory} bean with
     * {@code globaResources=true} in order to ensure the Reactor Netty global
     * resources are shut down when the Spring ApplicationContext is closed.
     *
     * @param factory the resource factory to obtain the resources from
     * @param mapper  a mapper for further initialization of the created client
     * @since 5.1
     */
    public ReactorClientHttpConnector(ReactorResourceFactory factory, Function<HttpClient, HttpClient> mapper) {
        this.httpClient = defaultInitializer.andThen(mapper).apply(initHttpClient(factory));
    }

    private static HttpClient initHttpClient(ReactorResourceFactory resourceFactory) {
        ConnectionProvider provider = resourceFactory.getConnectionProvider();
        LoopResources resources = resourceFactory.getLoopResources();
        Assert.notNull(provider, "No ConnectionProvider: is ReactorResourceFactory not initialized yet?");
        Assert.notNull(resources, "No LoopResources: is ReactorResourceFactory not initialized yet?");
        return HttpClient.create(provider).tcpConfiguration(tcpClient -> tcpClient.runOn(resources));
    }

    /**
     * Constructor with a pre-configured {@code HttpClient} instance.
     *
     * @param httpClient the client to use
     * @since 5.1
     */
    public ReactorClientHttpConnector(HttpClient httpClient) {
        Assert.notNull(httpClient, "HttpClient is required");
        this.httpClient = httpClient;
    }


    @Override
    public Mono<ClientHttpResponse> connect(HttpMethod method, URI uri,
                                            Function<? super ClientHttpRequest, Mono<Void>> requestCallback) {

        if (!uri.isAbsolute()) {
            return Mono.error(new IllegalArgumentException("URI is not absolute: " + uri));
        }

        return this.httpClient
                .request(io.netty.handler.codec.http.HttpMethod.valueOf(method.name()))
                .uri(uri.toString())
                .send((request, outbound) -> requestCallback.apply(adaptRequest(method, uri, request, outbound)))
                .responseConnection((res, con) -> Mono.just(adaptResponse(res, con.inbound(), con.outbound().alloc())))
                .next();
    }

    private ReactorClientHttpRequest adaptRequest(HttpMethod method, URI uri, HttpClientRequest request,
                                                  NettyOutbound nettyOutbound) {

        return new ReactorClientHttpRequest(method, uri, request, nettyOutbound);
    }

    private ClientHttpResponse adaptResponse(HttpClientResponse response, NettyInbound nettyInbound,
                                             ByteBufAllocator allocator) {

        return new ReactorClientHttpResponse(response, nettyInbound, allocator);
    }

}
